SCP-XXXX is to be kept within a lead strongbox and locked via two 4 digit padlocks, which are to be regularly changed on a weekly basis. The entity must be contained within a concrete dome, spanning 3 m tall at its center, and having a diameter of 7 m in width and length.

These containment procedures, as in the whole section of the article, are specific to a fault. While it is an initial assumption that being this precise and in-depth with the containment makes the section sound more scientific, the opposite is true. The portion of containment procedures boxed above implies that a containment breach will occur if:

There are more or less than 2 padlocks.

The entity is contained within a concrete box.

The cell is more or less than 3 meters tall, and/or more or less than 7 meters in width or length (diameter is usually mutually exclusive with the concepts of width and length).

four (4)

This is an outdated and improper numbering technique. It's origins, in real life, is in pharmaceutical prescriptions where this format was used so that prescriptions weren't tampered by the addition of zeroes. This is not a problem that a Foundation document is vulnerable to.

Due to the recent incident of #XXXX-02-Lambda all those afflicted with the entity's hazardous effects will be escorted by two (2) armed personnel, each having scored no less than a 7.2 on the IME (Indifference Monitoring Exam) and are fully expected to guard the affected personnel for the full 6 hour period.

Bolding text for the sake of emphasis looks forced and unprofessional. If this is a matter of emphasis, then try to use the words to convey that, namely feelings of severity, fear, etc. Bolding the text makes this blend into the section titles, and really looks out of nowhere. I recommend scrubbing this entirely as it suffers from the same problems found in the rest of this section.

SCP-XXXX is a plastic yellow game cartridge, with a blank, faded, label and containing the typical appearance of such cartridges.

This sentence can be tidied up. "SCP-XXXX is a yellow game cartridge with a blank, faded label." The picture already tells us that it looks like a normal cartridge and is made of plastic, and these are qualities that the reader naturally assume; the only reason to discuss these points is when the object breaks from the reader's assumption.

Another detail picked up by Researcher [REDACTED] was that the entity seemed to have predate the time period as to when video games were introduced, estimated to have existed for 60 years prior.

The description is not really the place to accredit pieces of information to specific personnel; it is the place to consolidate and present a description. Furthermore, the grammar falls completely apart after [REDACTED]. It should read something along the lines of "the object(avoid entity and try to use the widely used 'item/object') appears to have been created at least 60 years before the introduction of the first (cartridge?) video game."

SCP-XXXX-1

Splitting apart your description like this is inadvisable. It's not something that's done, and there's no real reason why this is kept away from the description. Most articles, even ones with multiple SCP instances, keep the description to its own section.

The description is also the place to describe the anomalous properties of your object. Leaving this information to addenda is rather unprofessional. Skimming the rest of the article, it appears that this is a game that, when played either compels people to violence or gives them fatal heart attacks. Both concepts, compulsion and 'thing-what-kills-you' have been heavily overdone and no longer serve as singularly reliable article foundations. Beyond the general grammar and tone fix-ups that I recommend you do, I also recommend getting the base idea polished up in the Ideas and Brainstorming Forum before you try fixing the draft. Go to that forum, post a quick summary of the concept you want to write up and the story(if present) you’re trying to tell (don't link the draft unless someone asks). The reviewers there can help you make pre-existing elements more interesting, chop out elements that aren’t interesting, and perhaps even propose new elements that improve the quality of your article. Good luck.